Foil thickness control apparatus



J. w. WALLACE FOIL THICKNESS CONTROL APPARATUS Filed Juhe 9, 1960 28 20SOURCE V 24 4 OF FLUID 3o CONTROL v X-RAY GAUGE =[L i I I l l I TENSION/5o 5 REGULATOR 54 TENSION REGULATOR VOLTAGE 44 REGULATOR as LIMITERINTEGRATING CIRCUIT CONTROL 36\ DEVICE PRE- 4s AMPLIFIER LIMITERPROPORTIONAL cun- CONTROL DEVICE PROPORTIONAL S 'NTEGRAL Q 3 CONTROL 2ERRggNTROL SIGNAL} 5 ERROR gslGNAL Z SIGNAL TIME TIME Fig. 2. Fig. 3.

WITNESSESI |NVENTQR QWMQQ C; John W. Wallace 'reference foil thickness.

United States Patent Filed June 9, 196% Ser. No. 34,943 4 Claims. (Cl.8032) The present invention relates to metallic foil thickness controlapparatus and more particularly to auto- 11121210 thickness or gaugeerror correcting control apparatus for a metallic foil rolling mill.

The control of foil strip thickness is extremely critical for a foilrolling mill due to the thickness of the foil being only in the order of.004 of an inch thick and less. Thusly, the maintenance of accurate foilstrip thickness or gauge without adversely affecting the rolling processis very diificult in that breakage and deformation of the foil strip isvery likely to occur.

it is an object of the present invention to provide improved thicknessrcontrol apparatus for a metallic foil rolling mill, wherein a moreaccurate control of the foil thickness or gauge is maintained relativeto a predetermined reference or desired foil thickness.

It is an additional object of the present invention to provide animproved thickness control apparatus for a foil rolling mill, wherein anoptimum control of the rolled foil thickness is provided with lessresulting variation or error in the rolled thickness relative to apredetermined reference or desired foil thickness.

It is a further object of the present invention to provide an improvedfoil rolling mill thickness control apparatus that has a bettererrorcorrection response characteristic and thereby gives a better and moreeven coil buildup on the rewind reel With less foil strip wander in therolls of the rolling mill.

These and other objects and advantages of the present invention willbecome apparent in view of the following description taken inconjunction with the drawings, wherein FIGURE 1 is a-diagrammaticshowing of the thickness contnol apparatus in accordance with theteachings of the present invention;

3,193,138 Patented Sept. 10, 1963 Ice and supplies it to each of anintegrating control device 38 and a proportional control device 40. Theintegrating control device 38 is operative in the manner of a motoroperated rheostat such that the output signal from the integratingcontrol device 38 varies in accordance with the time integral of theerror signal supplied by the X-ray gauge '32. A signal value limitercircuit 42 is connected between the integrating control device 38 and avoltage regulator .44 operative to control the operating speed of amotor 46 connected to the roller members 14 and 16.

The proportional control device 4% is operative to provide an outputsignal which varies proportional to and constant and predeterminedspeed.

FIG. 2 is a curve illustrating the operation of the proportion controldevice shown in FIG. 1; and

FIG. 3 is a curve illustrating the operation of the integrating controldevice shown in FIG. 1.

In FIG. 1, there is shown a rolling mill stand 10 for the rolling ofmetallic foil strip 11 which has a thickness in the order of 0.004 inch.The foil is supplied from an unwind reel 12 along a travel path betweenthe upper roller member 14 and lower roller member 16 of the foilrolling mill 10 to a rewind reel 18. The spacing between the rollermembers 14 and 16 is controlled by a suitable force member 20, which isillustrated as a cylinder 22 having a piston 24 therein which isconnected to apply force pressure to control the spacing between theroller members '14 and 16. A source of high pressure control fluid 26 isoperative through suitable control valves 28 and 3G for controlling theforce applied to determine the spacing between the roller members 14 and16. A well known X-ray gauge 32 is operative to measure the actualrolled thickness of the foil strip 11 leaving the rolling mill 10, andprovides a control signal in accordance with any error or differencebetween the actual rolled foil thickness and a predetermined desired orThe reference thickness may be manually set or determined by the settingof the X-ray gauge 32 by means of, for example, a manual control handle34.

The error signal from the X-ray gauge 32 is supplied to a preamplifier36 which amplifies the error signal in accordance with the instantaneousvariation of the error control signal received from the X-ray gauge 32.The output signal from the fast acting proportional control device 4% issupplied through a signal value limiter circuit 48 to a tensionregulator 59 operative to control the speed of a motor 52 connected tothe unwind reel 12. The voltage regulator 44 is operative with the millmotor 46 :to control the operation of the mill at a substantially Thetension regulator Si) is operative with the unwind reel 12 and its motor52 to control their operation for a pre-set strip tension by suitablechanges in the operation of the motor 52.

-A suitable tension regulator 54 is operative with a motor 56 connectedto the rewind reel 18 for providing a predetermined desired andsubstantially constant tension between the rolling mill 10 and therewind reel 18 relative to the foil strip 11 which leaves the rollingmill in and is wound. up as a coil on the rewind reel 18.

The curve of FIG. 2 illustrates the operation of the proportionalcontrol device 49 and is plotted in terms of signal magnitude as afunction of time. It will be seen from the curve of FIG. 2 that theerror signal is operative with the proportional control device 40 toprovide a control signal which varies substantially in accordance withthe instantaneous variation of the error signal.

In FIG. 3 the curve illustrates the operation of the intergratingcontrol device 38 such that the error signal which is plotted in termsof signal magnitude as a function of time is operative with theintegrating control device 33 to provide a control signal which is theeffective integral of the error signal.

Thusly, in the case of an error signal which is removed due to thecorrecting operation of the present control apparatus, the controlsignal supplied by the proportional control device would return to aZeno value, where-as the integral control signal supplied by theintegrating control device 38 would have a finite value in accordancewith the effective integral of the error signal as a function of time.

In the operation of the control apparatus as shown in FIG. 1, the X-raygauge 32 is operative to provide an error signal in accordance with anyerror or difference in the actual rolled foil thickness, as measured bythe X- ray gauge 32 relative to a predetermined desired or referencefoil thickness as determined by the setting of the manual handle 34.This error signal is supplied through the preamplifier 36 to each of theintegrating control device 38 and the proportional control device 40.

The integrating control device 38 is operative as a slow responding andhighly accurate integral control system that is operative as a zeroerror system and controls the operating speed of the mill, hence thefriction of the mill, to maintain a very accurate average foilthickness. The proportional control device 40 is a fast respondingproportional control device and operates into the unwind reel tensionregulator to correct for fast changes in foil thickness or gauge toreduce the amplitude of the thickness or gauge deviation relative to thedesired or reference thickmess. The limiter circuits 42 and 48 areoperative to limit and thereby provide a maximum correction signal tothe respective voltage regulator 44 and tension regulator 50.

The combination of the slow responding and highly accurate integralcontrol device 38 with the fast responding proportional control device40 provides an optimum control system for the control of rolled foilthickness or gauge. tional control device 40 being operative only withthe unwind reel 12 tension regulator provides a correction for fastchanges in foil strip thickness or gauge to thereby reduce the amplitudeof such errors or changes, and the slower acting integrating controldevice 38 is operative as a zero error device and corrects only theoperating speed of the rolling mill through the voltage regulator 44 andthe mill motor 46. The integrating control device 38 works only on millfriction to maintain a very accurate average rolled coil thickness.tegrating control device 38 responds slowly enough that the tensionregulator 54 for the rewind reel 18 can follow its corrections, there isno problem regarding the buildup of a good coil of foil strip on therewind reel 18.

It is necessary that the thickness control operation is very closelycoordinated With the operation of the rewind reel 18, since fast changesof the rolling mill speed will cause the foil strip to Wanderundesirably in the roll members 14 and 16 and further to result in anuneven buildup of the coil on the rewind reel 18. This uneven buildup isin the form of a mismatch between successive layers of the coil on therewind reel 18. In actual practice, it is extremely difiicult and notpractical to precisely coordinate the speed of the rolling mill 10 vandthe operation of the rewind reel 18 Well enough to obtain an advantagefrom fast control of the operating speed of the rolling mill 10 throughfast or rapid controlling of the operating speed of the mill motor 46.However, the operation of the rolling mill 10 itself is less sensitiveto fast changes in the operating speed of the unwind reel 12 due to fastcorrection of theoperating speed of the motor 52 of the unwind reel 12,and such changes in the operation of the motor 52 connected to theunwind reel 12 do result in correcting the rolled thickness of the foilstrip leaving the roller members 14 and 16. Further, fast changes in theoperating speed of the motor 52 connected to the unwind reel 12, forexample changes taking place in one second of time or less, do not causeundesirable wandering of the foil strip between the roller members 14and 16, nor do such fast changes cause loss of desired tension betweenthe rolling mill 10 and the rewind reel 18. Thusly, no coil layertelescoping or uneven buildup of the coil on the rewind reel 18 results.In this manner the tension between the unwind reel 12 and the rollingmill 10 can be changed quite rapidly to vary and correct the thicknessor gauge of the rolled foil strip without adversely affecting the otherfactors in the rolling process.

A typical foil rolling mill includes a single stand such as the rollingmill 10 and it has been found in actualrpractice that a superioroperation of a foil rolling mill results when the fast actingproportional control device 40 is operative to control the tension ofthe foil strip between the 'unwind reel 12 and the roller members 14 and16 of the foil rolling mill 10, in combination with a slower actingintegrating control device 38 operative to control the speed of the millmotor 46 connected to the roller members 14 and 16 of the foil rollingmill.

For a prior art teaching of each of the proportional control device andthe integrating control device, reference may be made to a book entitledElectronic Analog Computers by Korn and Korn, 2nd Edition, published bythe McGraw-Hill Book Co. in 1956, and particularly pages 175 to 184.

While one preferred embodiment of this thickness control apparatus is tohave the proportional control device 40 be operative with the unwindreel 12 tension regulator 50 and to have the integrating control device38 be Thusly, the combination of the fast acting propor- 7 Because theinoperative to control the speed of the rolling mill 10 through thevoltage regulator 44, it is clearly within the scope of the presentteachings to connect the integrating control device 38 to be operativefor controlling either one of the strip tension through the tensionregulator 50 for the reel motor 52 or the speed of the rolling mill 10through the voltage regulator 44, and to connect the proportionalcontrol device 4% to be operative for controlling the other of saidspeed of the rolling mill 10 through the voltage regulatorv 4-4 for themill motor 46 or said strip tension through the tension regulator 50, asmay be desired.

Although the present invention has been described with a certain degreeof particularity, it should be understood that the present disclosurehas been made only by way of example and thatnumerous changes in thedetails of construction and the combination and arrangement of parts maybe resorted to without departing from the scope and the spirit of thepresent invention.

I claim as my invention:

1. In control apparatus fora foil rolling mill having a roll memberdriven by a first motor and including a tension controlling devicehaving a second motor, the combination of signal providing meansoperative with the foil leaving said mill for providing a thicknesserror signal in accordance with the actual foil thickness compared to adesired reference foil thickness, first thickness control meansoperative with only one of said first and second motors for varying thespeed of said one motor as a substantially direct proportional functionof said error signal, and second thickness control means operative withonly the other of said first and second motors for controlling saidother motor as a predetermined rate integral of said error signal.

2. In thickness control apparatus for a foil rolling mill including amill speed controlling motor and a foil ten ,sion controlling motor, thecombination of signal providing means operative with the foil at apredetermined location relative to said mill for providing a thicknesserror signal having a magnitude variation in accordance with the actualfoil thickness relative to a desired reference foil thickness, firstthickness control means operative with only said tension controllingmotor for varying the operation of said tension controlling motor as adirectly proportional function of the magnitude of said error signal,and second thickness control means operative only with said mill speedcontrolling motor for varying the operationof said mill speedcontrolling motor as a predetermined rate function of the variation ofsaid error signal, with said first thickness control means being fasteracting than said second thickness control means.

3. In thickness control apparatus operative with a metallic foil rollingmill having a troll member driven by a first motor and including atension controlling reel member driven by a second motor, thecombination of error signal means operative with said rolling mill forproviding an error signal having a magnitude in accordance with thedifference between the actual thickness of the foil leaving the rollingmill and a predetermined desired foil thickness, a first control deviceoperative only with one of said first motor and said second motor andbeing responsive to said error signal for controlling the operation ofsaid one motor as a substantially proportional function of the magnitudeof said error signal, and a second control device operative only withthe other of said first motor and said second motor and being responsiveto said error signal for controlling the operation of said other motoras a pre determined integral of said error signal, with said secondcontrol device being slower acting than said first control device.

4. In thickness control apparatus for a foil rolling mill driven by amill roll motor and including a tension controlling motor, thecombination of signal providing means operative with the foil at apredetermined location relative to said mill for providing a thicknesserror signal having a magnitude variation in accordance with the acReferences Cited in the file of this patent tual foil thickness relativeto a desired reference foil thickness, first thickness control meansoperative with TED STATES PATENTS only said tension controlling motorfor varying the operation of said tension controlling motor as adirectly pro- 5 2264096 Mohler 1941 portional function of the magnitudeof said error signal, 2542790 Cook 1944 and second thickness controlmeans operative only with 2,830,249 Peters)? P 3, 1958 said mill motorfor varying the operation of said mill 2,851,911 Hessennefg P 1953 motoras a predetermined rate function of the variation 2,933,626 Giboney eta1 P 1960 of said error signal. 10 2,972,269 Wallace et a1 Feb. 21, 196]

1. IN CONTROL APPARATUS FOR A FOIL ROLLING MILL HAVING A ROLL MEMBERDRIVEN BY A FIRST MOTOR AND INCLUDING A TENSION CONTROLLING DEVICEHAVING A SECOND MOTOR, THE COMBINATION OF SIGNAL PROVIDING MEANSOPERATIVE WITH THE FOIL LEAVING SAID MILL FOR PROVIDING A THICKNESSERROR SIGNAL IN ACCORDANCE WITH THE ACTUAL FOIL THICKNESS COMPARED TO ADESIRED REFERENCE FOIL THICKNESS, FIRST THICKNESS CONTROL MEANSOPERATIVE WITH ONLY ONE OF SAID FIRST AND SECOND MOTORS FOR VARYING THESPEED OF SAID ONE MOTOR AS A SUBSTANTIALLY DIRECT PROPORTIONAL FUNCTIONOF SAID ERROR SIGNAL, AND SECOND THICKNESS CONTROL MEANS OPERATIVE WITHONLY THE OTHER OF SAID FIRST AND SECOND MOTORS FOR CONTROLLING SAIDOTHER MOTOR AS A PREDETERMINED RATE INTEGRAL OF SAID ERROR SIGNAL.